This study aims to test the effectiveness of a single intravenous (IV, through the vein) dose of the study drug, bevacizumab (Avastin), in preventing/reducing the development of Acute Respiratory Distress Syndrome (ARDS), in patients with severe sepsis, who are at high risk for developing ARDS. ARDS is a lung disease caused by a lung injury that leads to lung function impairment. The condition the patient has,severe sepsis, is a medical condition associated with an infection characterized as an immune system inflammatory response throughout your whole body that can lead to organ dysfunction, low blood pressure or insufficient blood flow to one or more of your organs.